Always prioritize safety when working with gas appliances. Before starting, ensure adequate ventilation, and if you smell gas, immediately turn off the gas supply, evacuate the area, and call your gas company or a professional plumber. Never attempt to troubleshoot if you suspect a gas leak; this project assumes no active gas leak.

You'll definitely need a reliable flashlight, like the Panther Vision FLATEYE, to inspect dark areas. For cleaning connections, fine-grit sandpaper (e.g., Fandeli 400 Grit) and a scour pad are useful. If you suspect a faulty thermocouple, have a new resideo 30 Millivolt Universal Gas Water Heater Thermocouple ready, along with an adjustable wrench set for replacement.

The most frequent cause of a gas water heater not producing hot water that beginners should check is a pilot light that has gone out. This is often an easy fix, requiring you to relight it according to your water heater's instructions. If the pilot light won't stay lit, the thermocouple is the next most common culprit to inspect and potentially replace.

Most troubleshooting steps, like checking the pilot light or cleaning the thermocouple, can be done within 30-60 minutes. If you need to replace the thermocouple, it might take an additional hour for purchase and installation. A new thermocouple (like the resideo CQ100A1013) typically costs around $15-$30, making this a very cost-effective DIY repair compared to a professional service call.